Galectin-1 (Gal-1), is a carbohydrate-binding protein with affinity for b-galactose. Gal-1 is involved in cell adhesion, migration, and apoptosis. In addition, Gal-1 has been found to be associated with a variety of cancers. Several groups have demonstrated that melanoma cells secrete an abundance of Gal-1. This observation taken together with Gal-1's well-known pro-apoptotic and immunoregulatory effects on helper T cells has led to the hypothesis that Gal-1 elicits tumor-immune escape mechanisms by inducing immunosuppression on melanoma antigen-specific CD8+ T cells. The long-term goal of this project is to study the efficacy of eliminating Gal-1 ligands on melanoma antigen-specific CD8+ cytotoxic T cells (CTLs) in an adoptive T cell therapy setting. Currently, adoptive CD8+ T cell therapy has shown modest improvements in patients with advanced melanoma. Thus, blocking Gal-1-Gal-1 ligand interactions on antigen-specific CTLs, prior to adoptive immunotherapy, could help avoid current shortcomings, such as T cell susceptibility to tumor-derived Gal-1, thereby enhancing anti-tumor efficacy. To this end, my goals are to determine whether CTLs lacking Gal-1 ligands can effectively attenuate tumor growth in an autologous adoptive T cell transfer setting. Results from these studies will greatly impact efforts to improve adoptive immunotherapy for treating cancer. Specific Aim 1. Published studies demonstrate that Gal-1 has immunoregulatory effects on T helper cells. However, few studies have been published about the role of Gal-1 on CD8+ T cells. My preliminary data establish that CTLs express Gal-1 ligands and undergo Gal-1-mediated modulation. Furthermore, we show that Gal-1 expression is correlated to disease progression and ineffective CD8+ T cell responses. These data has led to the hypothesis that Gal-1 suppresses CTLs contributing to tumor immune escape. To test this hypothesis, I will analyze the effects of Gal-1-mediated cytokine expression, proliferative potential and apoptotic activity on antigen-specific CTLs. Specific Aim 2. Studies in my lab have demonstrated that treatment of B16 tumor-bearing mice with Gal-1 ligand inhibitor, 4-F-GlcNAc, and results in anti-tumor activity2. 4-F-GlcNAc has anti-carbohydrate effects on many types of immune cells, so I plan to devise a more focused treatment. I will treat CTLs ex vivo with 4-F-GlcNAc and then transfer the cells into tumor-bearing mice. I hypothesize that CTLs treated with 4-F-GlcNAc will be spared from Gal-1-mediated cell death and suppression, thus increasing CTL levels and enhancing anti-tumor activity. To test this hypothesis, I will analyze for cell viability and cytokine expression using FACS and ELISA in 4-F-GlcNAc treated and untreated CTLs. I will also study the anti-tumor efficacy of the transferred CD8+ T cells in melanoma-bearing mice. Overall, my data will explore the therapeutic utility of CTLs treated with 4-F-GlcNAc in adoptive T cell immunotherapy.